Jeff Immelt moved one step closer to selling NBC Universal to Comcast after he hammered out a tentative agreement to buy out French partner Vivendi’s 20 percent stake in the media giant for $5.8 billion.

While it had been seen as a given that Vivendi would sell its stake in NBC to GE, the process had been stymied somewhat as Vivendi appeared to be holding out for as high a price as possible and GE tried to buy back the stake on the cheap.

With GE and Vivendi now on the same page, sources said a deal could be unveiled within a week, though regulatory approval could take a year.

An agreement was reached after Immelt, GE’s chairman and CEO, held face-to-face talks in Paris with Vivendi CEO Jean-Bernard Levy last week, which helped close a gap in price that reached nearly $1 billion.

GE also agreed to pay Vivendi as much as $2 billion if the separate GE-Comcast transaction doesnt close by the end of 2010, said one of the people. Vivendi had been seeking an up-front payment to protect the company in case regulators scuttled the deal, Amobi said.

Initially, GE had offered to buy back the stake for $5 billion, well below the $6 billion value that Comcast and GE had negotiated when the two companies agreed NBCU was worth $30 billion.

However, the power soon tilted in Vivendi’s favor as it became clear a GE-Comcast deal could not be completed without Vivendi’s OK.

GE and Comcast have been in talks for weeks about a deal in which NBCU would be combined with Comcast’s content assets, which include the E!, Style and Golf channels, to create a new entity.

Comcast would contribute around $6 billion in cash in return for a 51 percent stake. GE would own the balance but have an option to sell the stake back to Comcast in 3½ years after the deal’s completion and again at its seventh anniversary.